Browse Topic: Air cooled engines
Fuel cell technology is gaining prominence as a clean, efficient, and scalable power solution for electric mobility, addressing key limitations of conventional battery systems such as long charging times, limited range, and declining performance in high-utilization applications. Proton Exchange Membrane Fuel Cells (PEMFCs) offer high energy density, rapid refueling, and robust operation under varying load conditions, making them particularly suitable for light electric vehicles such as two-wheelers, e-rickshaws & range extenders. Within the broader category of PEMFCs, air-cooled fuel cells present unique advantages for mobility applications. Their simplified architecture eliminates the need for complex liquid cooling systems, leading to lower system weight, reduced component count, and easier integration. This translates into a compact, lightweight, and cost-effective power unit—ideal for vehicles where space, weight, and maintenance constraints are critical. The market for air-cooled fuel cells is expanding globally, driven by demand for lightweight and portable mobility solutions. Specific application segments include electric two-wheelers (300–500 W), which are rapidly gaining ground in Asian markets; e-rickshaws (2–3 kW), a promising Indian market segment seeking alternatives to fossil fuel and lead-acid battery systems. Additionally, the system is well-suited for use as a range extender in electric mobility platforms, offering extended operational duration without compromising on vehicle packaging or efficiency. This work presents an indigenously developed air-cooled PEMFC system designed specifically for low power mobility applications. Indigenous Pt/C catalyst for fuel cell application which meets DoE durability target (30k AST cycles) has been developed. The stack comprises of an innovative flow field configuration for uniform reactant distribution, and advanced thermal management strategy that ensures efficient heat dissipation. The indigenously developed fuel cell stack tailored for Indian weather conditions (5°-45°C, 30-100% RH) achieves critical performance targets including high power density (400-500 W/L), small footprint & mass (600-700 W/kg) at par with leading commercial fuel cell solution providers. This development signifies a critical step toward self-reliant, sustainable, and high-performance power solutions for next-generation electric & green mobility in India and beyond
This document is reissued for application to helicopters.
Collaborative research outlined in this paper documents recent engine and emission performance of a newer, more robust small SI engine across a sweeping range of relative humidity (RH) having fixed intake air temperature and pressure. The experimental results will show that power correction references to SAE J1349 as well as humidity correction (Kh) reference in EPA 40 CFR §1065 may generically be applied, but do not accurately compensate for the extent of correction required. The test results shared from this particular performance testing of a Kohler KT745 carbureted engine develops the case for a more diverse and less conservative approach to a one-size-fits all strategy related to humidity corrections within the small SI testing community. Moreover, humidity effects for both observed and corrected power, as well as emission corrected constituents (not just NOx) are generally greater than would otherwise be assumed from the literature. From these results, facilities without intake air humidity management may unknowingly bias brake specific emissions of both HC+NOx and CO family emission limits (FELs). Moreover, in defining family emission limits with NOx only correction, general performance repeatability in certifications as well as production line testing (PLT) results throughout the year may contribute to a wider deviation in engine-to-engine emission variability and power than might normally be expected. The following results are specifically for rich engine operation of an air-cooled engine, and subsequent results for stoichiometric air-cooled engine relative humidity effects would need to be discussed separately.
This SAE Aerospace Information Report (AIR) has been written for individuals associated with the ground-level testing of large and small gas turbine engines and particularly for those who might be interested in upgrading their existing or acquiring new test cell facilities.
This SAE Aerospace Information Report (AIR) has been written for individuals associated with the ground-level testing of large and small gas turbine engines and particularly for those who might be interested in upgrading their existing or acquiring new test cell facilities.
Traditionally, most charge air coolers (CACs) have been constructed using the Nocolok aluminum brazing process. The Nocolok process uses flux, some of which remains after the manufacturing process, and migrates through the intake tract to the engine during normal use. This migration and deposition on engine components can cause a variety of issues with engine operation. Currently the only alternative to Nocolok brazed CACs for engines sensitive to flux migration is vacuum brazing, which comes at a significant price increase. In the effort to reduce cost and increase efficiency, there is interest in whether a Nocolok brazed CAC with a reduced amount of flux residue can be successfully applied to flux-sensitive engines. This paper compares the impacts of Nocolok flux migration on engine hardware between a traditional Nocolok brazed CAC versus a Nocolok brazed CAC with a reduced amount of flux residue using a simulated vehicle operation test and its analysis, and examines whether a CAC with reduced flux residue can potentially be used in a flux-sensitive application.
This document discusses formulae considered applicable to aircraft engines having integral supercharging without aftercooling, and using gasoline introduced at the entrance to the supercharger or directly into the cylinders. Such engines are normally designated as single and two speed engines. Correction formulae for engines having two stage or exhaust turbo supercharging will not be discussed. Corrections for engines having a high degree of integral supercharging will be discussed in general terms only and no specific formulae will be presented. The correction formulae and methods listed are empirical and subject to error due to conditions beyond the scope of known corrections. Usage has indicated, however, that the correction formulae listed will provide a satisfactory approximation of power output under standard conditions.
In the early 1980's, some promising research and development efforts focused on powder metallurgy revealed that aluminum alloys containing 4 wt% cerium exhibit high temperature mechanical properties exceeding those of the best commercial aluminum casting alloys currently in production. Cerium oxide is an abundant rare earth oxide that is often discarded during the refining of more valuable rare earths such as Nd and Dy. Therefore, the economics are compelling for cerium as an alloy additive. In this paper, we report select results obtained during an investigation of the castability of aluminum-cerium alloys and determine compositional modifications that may be required to ensure the compatibility of the alloy with near net shape casting methods such as advanced sand casting, die casting, permanent mold casting and squeeze casting. Al-Ce alloys were cast in binary composition of 6-16 wt% Ce. Commercially pure aluminum ingots were melted and held at approximately 785°C. Ternary and quaternary alloys with Si and Mg additions were also investigated. Test bars were cast to establish mechanical properties and step plates and hot tear molds were used to determine sensitivity to solidification conditions and hot tearing sensitivity respectively. Finally, air cooled engine cylinder heads were cast in sand molds to get a sense of castability in complicated shape castings.
The performance and exhaust emissions of a commercially available, propane fueled, air cooled engine with Electronic Fuel Injection (EFI) were investigated by varying relative Air to Fuel Ratio (λ), ignition timing, and Compression Ratio (CR). Varying λ and ignition timing was accomplished by modifying the EFI system using TechniCAL Industries’ engine development software. The CR was varied through using pistons with different bowl sizes. Strong relationships were recorded between λ and ignition timing and the resulting effect these parameters have on engine performance and emissions. Lean operation (λ > 1) has the potential to significantly reduce NOx production (110 g/kW-hr down to 5 g/kW-hr). Unfortunately, it also reduces engine torque by up to an order of magnitude (31 Nm down to 3 Nm). Moving ignition initiation to earlier in the compression stroke, 10o to 40o Before Top Dead Center (BTDC), improved engine performance considerably (25% improvement in brake torque) in the presence of excess air. Unfortunately, advancing the ignition also caused NOx production to increase. The effects these parameters have on engine performance are significant enough that the same engine can be used for vastly different applications with changes only to the control software. Compression ratio has a less significant effect on engine performance, but increasing CR does result in an increase engine torque. Increasing CR from 9.1:1 to 11:1 resulted in an increase in engine torque of approximately 10% for the operating parameters tested.
Still today, two-stroke engine layout is characterized by a wide share on the market thanks to its simpler construction that allows to reduce production and maintenance costs respecting the four-stroke engine. Two of the main application areas for the two-stroke engines are on small motorbikes and on handheld machines like chainsaws, brush cutters, and blowers. In both these application areas, two-stroke engines are generally equipped by a carburettor to provide the air/fuel mixture formation while the engine cooling is assured by forcing an air stream all around the engine head and cylinder surfaces. Focusing the attention on the two-stroke air-cooling system, it is not easy to assure its effectiveness all around the cylinder surface because the air flow easily separates from the cylinder walls producing local hot-spots on the cylinder itself. This problem can be bounded only by the optimization of the cylinder fin design placed externally to the cylinder surface. In the present paper the authors present a first analysis of the thermal-flow behaviour of a two stroke engine designed for brush-cutter machine applications. The optimization of the air-cooling system of such a machine is a very challenging task because the machine design is very compact forcing all the engine parts to remain quite close to each other. The proposed analysis is performed by the definition of a specific 3D-CFD simulation methodology based on the Conjugated Heat Transfer approach. The methodology was validated against experimental data.
Small power diesel engines are most demanding product in Indian market for stationary applications like power genset, agricultural purpose etc. The upcoming 2013 CPCB emission norms for diesel genset engines below 19 kW power rating are the most stringent one in the world. There is a need not only to upgrade technologies pertinent to the latest emission norms but also to reduce the product cost. This paper presents various design strategies used to meet the desired engine performance and emission levels for development of a series of small power diesel genset engines having bore dia. ranging from 76 mm to 120 mm. Design and development of single and two cylinder NA diesel engines has been carried out with the help of CAD/CAE, design analysis tools, in-house developed algorithms and available statistical database Simulation codes are used for design analysis of engine subsystems like valve train, power train and flow analysis of air cooled engine in order to make the product technically and economically viable. Design verifications performed on several engine systems and sub-systems have been presented in the paper
This document discusses formulae considered applicable to aircraft engines having integral supercharging without aftercooling, and using gasoline introduced at the entrance to the supercharger or directly into the cylinders. Such engines are normally designated as single and two speed engines. Correction formulae for engines having two stage or exhaust turbo supercharging will not be discussed. Corrections for engines having a high degree of integral supercharging will be discussed in general terms only and no specific formulae will be presented. The correction formulae and methods listed are empirical and subject to error due to conditions beyond the scope of known corrections. Usage has indicated, however, that the correction formulae listed will provide a satisfactory approximation of power output under standard conditions.
Engine life and effectiveness can be improved with effective cooling. In designing and optimization process, simulation plays a vital role. The cooling mechanism of the air cooled engine is mostly dependent on the fin design of the cylinder head and block. The heat is conducted through the engine parts and convected to air through the surfaces of the fins. Insufficient removal of heat from engine will lead to high thermal stresses and lower engine efficiency. To simulate the cooling mechanism of the naturally aspirated engines, Three Dimensional CFD analyses with the SC/Tetra code is done. This gives a good scope in analyzing the existing fin design and proposes the optimized design. The boundary conditions required for carrying the CFD analysis such as the heat transfer co-efficient, cylinder temperature, has been generated by carrying One Dimensional engine cycle simulation. Engine assembly is imported into SC/Tetra code and conjugate heat transfer analysis is conducted to understand the effectiveness of heat transfer through the fins. Conjugate heat transfer analysis provides a clear view on heat transfer through solid and fluid domain. Detailed study on the heat transfer of the cylinder head and block has been done. Fin increases the convective heat transfer rate. A detailed parametric study of heat transfer on fins is done and Theoretical analysis has been carried out to achieve an optimal fin design for effective heat transfer. Theoretical analysis aids in speeding up the design optimization problem. Conjugate heat transfer analysis of engine assembly with modified fins is performed. The results of heat transfer through the existing fins and modified fins are compared. There is a considerable increase in the heat transfer with the modified fins. A methodology for optimizing the fin heat transfer and fin performance is proposed.
The China III stage today represents the most stringent motorcycle emission rule in the world, mixing the European standards for tailpipe emissions with the United States rules for durability and evaporative emissions. On the other hand Chinese vehicles are based on small engines that ask for affordable, compact and simply solutions. This scenario drove Dell'Orto to develop a tailored engine management system, leading to a new generation of the existing electronic carburation system ECS, that features an oxygen sensor closed-loop control as well as a throttle contactless linear sensor. This paper presents the development of the second generation ECS for two- and three-wheeler Chinese vehicle application. System conceptualization, components design, control strategies, experimental development and durability testing are shown for a single cylinder air cooled engine application. According to the operating condition and the driver demand, the air to fuel ratio AFR is pre-set by means of a proportional control electrovalve. A closed coupled oxygen switching sensor then detects the resulting AFR. According to this feedback signal the electronic control unit ECU adjusts the driving signal of the AFR control electrovalve, in order to match the stoichiometric conditions. This allows to miximize the three-way catalytic converter efficiency, without using secondary air system. The closed coupled oxygen sensor doesn't need a heating circuit, since it uses the hot exhaust gases to heat up itself quickly. The oxygen sensor feed-back control is used also during the transient operation of the emission test cycle, improving the catalyst performance. Moreover the ECS closed-loop control technique allows to bias from stoichiometric AFR, enhancing the emissions, driveability and fuel economy trade-off. Regarding the durability issue, the closed loop control self compensates engine ageing, keeping the AFR at its target level. A new linear throttle sensor, with contactless technology, assure a robust and durable behavior. The throttle sensor auto-zeroing strategy is implemented to compensate the idle deviation during engine lifetime. Embedded recovery strategies allow engine operation in case of sensors or actuators failures, flashing the malfunction indicator lamp for easy service diagnosis. Thanks to the closed-loop control, the ECS can compensate not only engine ageing but also production variability as well as different fuels, filter clogging, environmental condition, etcetera. The aim of closed-loop ECS is to simply replace the existing carburetors and ignition modules, with no need to re-design the engine. The electronic carburetor is interchangeable with the previous one, while the ECU replaces the ignition control module. Existing flywheel generators can be used since the electric absorption of the ECU and the AFR control electrovalve is very low. Compared to a fuel injection system the ECS gives the same performance without electric fuel pump and toothed flywheel. Furthermore the ECS is compatible with kick-start as well as battery-less application, concept that can be interesting for many other small engine applications rather than two- and three- wheeler.
With the interest in global environmental issues growing in recent years, the demand for the reduction of exhaust gas emission and improvement in fuel consumption for small motorcycles has increased greatly. Recently, small motorcycles have been marketed equipped with an electronically controlled fuel injection system effective in reducing emissions and enhancing fuel consumption by accurately controlling the air-fuel ratio. The small motorcycles' market comprises mainly ASEAN countries, and the majority of the motorcycles consist of reasonably priced models with air-cooled engines. Fuel injection systems have already been adopted for motorcycles equipped with water-cooled engines in the markets of advanced countries, mostly in EU. Given the above situation, two issues must be addressed to adopt a successful fuel injection system for air-cooled, low-priced small motorcycles. First, the fuel injection systems' components must be protected from the thermal influence of air cooled engines. Due to higher ambient temperatures around the air cooled engine as compared to the water-cooled engine, vaporization of fuel must be prevented. Second, the cost of the fuel supply system must be minimized to permit manufacturing of a low price motorcycle. The developed fuel injection system has addressed above-mentioned issues with modifications of the major component parts of the fuel feed system, the fuel pump module, high-pressure fuel piping and injector, and by eliminating the return pipe from fuel feed system. This paper presents details of design technologies employed to create each component and the results obtained from a performance test of a comparing vehicle, 125 cm3 motorcycle.
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