Recently, the use of air conditioning systems is growing rapidly due to increasing global temperatures. Considering enormous growth in the application of the air conditioning system, there is an urgent need to improve design, performance, and efficiency thereof. For example, the air conditioning systems that are being used these days are required to provide improved efficiency per unit of power consumed, and they are also required to have a smaller form factor as compared to conventional air conditioning systems. Therefore, a lot of modern air conditioning systems employ components such as internal heat exchangers, thermal expansion valves and forth to improve their performance while having a small form factor. In this study a condenser is adapted to be used for an air conditioning system employing an internal heat exchanger. Wherein the condenser subcool area is in a optimized range of a frontal condenser area; and a free flow area within the plurality of tubes of the subcool region of the at least one refrigerant flow section for the refrigerant flow within the plurality of tubes…

Abstract The Thermal Management of Electric Vehicles differs strongly from the Thermal Management in IC engine driven vehicles. The Air Conditioning Circuit itself has comparable requirements, however, the electric components and their properties lead to new architectures. Essential is at least a chiller for the conditioning of the battery, which needs to be cooled down to the range of summer ambient temperatures. The respective control devices need to fulfill different basic requirements - Small package - Lightweight - Low noise - Low energy consumption - High control accuracy to play an important role in the Refrigeration architecture of Electric and Hybrid Vehicles. For conventional systems, optimization of package and weight will be achieved by a 75g TXV with a 28 mm thermal head. As soon as a battery also has to be cooled, Shut-Off valves will be implemented in the system in order to manage the respective heat loads according to the needs. For some system configurations, it is important to have a precise electronic control, which is not following the usually fixed superheat characteristic…

For years, researchers have presented numerous studies that consider interaction between working fluid and reed valve motion in displacement compressors. The computing capacities and available CFD and FEA simulation tools have allowed modeling of fully coupled interaction of fluids and moving structures. The present paper describes our experience and results from developing a simplified model of a multi-cylinder reciprocating piston compressor and estimation of pressure surge during sudden acceleration of such compressors. The results show that sudden speed change causes surge in pressures due to formation of pressure waves that reflect back and forth within cylinder. For the chosen geometry and operating conditions, the duration of such waves is much shorter (~ 0.2ms) as compared to longer response time of reed valves (1 ms) that are stiff and highly inelastic. These high pressure waves eventually exceed the fatigue limit of reed valves and cause failures. These pressure waves also influence the performance of reciprocating by causing noise and vibrations which eventually dissipate in to heat thereby lowering the COP of compressor. Simulation results compare well…

With the advent of new technologies and rigorous research and development in engines, cars are becoming quieter than ever. This has led to the noises which were earlier, masked behind engine noise being audible inside the passenger compartment. Having a quieter air-conditioning (AC) system would aid us in cutting down on this parasitic noise source. Making it one of the important parameters during the design and development of the Heating, Ventilation and Air-Conditioning (HVAC) system for a vehicle program. However, due to packaging constraints improper integration or selection of different AC parts, there is a possibility that the noise generated from the AC compressor to get amplified while the refrigerant flows through the thermal expansion valve (TXV) or through pipes. This is because the pressure pulsation, in the refrigerant flow, travels along the pipes and can amplify the noise if it is not properly dampen out. Also, TXVs can also be a source for noise if the quality of refrigerant - dryness fraction - is not optimized at the entry. The objective of the current…

In an Adaptive Cycle Engine (ACE), thermodynamics favors combustion starting while the compressed, premixed air and fuel are still flowing into the cylinder through the transfer valve. Since the flow velocity is typically high and is predicted to reach sonic conditions by the time the transfer valve closes, the flame might be subjected to extensive stretch, thus leading to aerodynamic quenching. It is also unclear whether a single spark, or even a succession of sparks, will be sufficient to achieve complete combustion. Given that the first ACE prototype is still being built, this issue is addressed by numerical simulation using the G-equation model, which accounts for the effect of flame stretching, over a 3D domain representing a flat-piston ACE cylinder, both with inward- and outward-opening valves. A k-epsilon turbulence model was used for the highly turbulent flow field. It was found that the flame would suffer local blow-off under most operating conditions, but the blow-off is never complete so that the regions affected are later re-ignited by the remaining parts of the flame, and combustion…

In a hydraulic system, parameter variation, contamination, and/or operating conditions can lead to instabilities in the pressure response. The resultant erratic pressure profile reduces performance and can lead to hardware damage. Specifically, in a transmission control system, the inability to track pressure commands can result in clutch or variator slip which can cause driveline disturbance and/or hardware damage. A variator is highly sensitive to slip and therefore, it is advantageous to identify such pressure events quickly and take remedial actions. The challenge is to detect the condition in the least amount of time while minimizing false alarms. A Neyman-Pearson and an energy detector (based on auto-correlation) are evaluated for the detection of pressure disturbances. The performance of the detectors is measured in terms of speed of detection and robustness to measurement noise. The implications in terms of computations and memory utilization of implementing the detectors in real-time embedded systems are also discussed. Both simulation and hardware examples are presented. The hardware experiment is performed in a hydraulic system with low damping composed of a solenoid…

As greenhouse gas regulations continue to tighten, more opportunities to improve engine efficiency emerge, including exhaust gas heat recovery. Upon cold starts, engine exhaust gases downstream of the catalysts are redirected with a bypass valve into a heat exchanger, transferring its heat to the coolant to accelerate engine warm-up. This has several advantages, including reduced fuel consumption, as the engine’s efficiency improves with temperature. Furthermore, this accelerates readiness to defrost the windshield, improving both safety as well as comfort, with greater benefits in colder climates, particularly when combined with hybridization’s need for engine on-time solely for cabin heating. Such products have been in the market now for several years; however they are bulky, heavy and expensive, yielding opportunities for competitive alternatives. Customer voice expresses needs for less complex designs that reduce package space, mass and part count (i.e. cost) while maintaining or improving performance, including the integration of an active bypass control valve. This paper highlights the design of an exhaust heat recovery system including relative benchmarking of commercially available products, comparing various aspects of…

This IC engine improvement addresses ICE’s inherent efficiency limit through innovative mechanical design of a consolidated system encompassing intake bypass and coordinating injection mechanism. In principle, the exhaust energy is recuperated to modulate intake temperature, in the meantime, multi-staged injection control is proposed that enhances in-cylinder thermal efficiency. To be specific, a CFD-optimized bypass is constructed alongside the intake and injection design which utilizes multi-stage variable mixing precisely, taking full advantage of exhaust temperature elevation. Regenerative heat gained through exhaust system gives rise to flexible amount of thermal dynamics adjustment to the intake, which consequently delivers more robust combustion efficiency as well as lower emission metrics. A flow control valve is developed at intake interface enables modular variable intake routing supporting engine efficiency promotion. To improve power density and engine emissions, we develop a multiple injection strategy in accordance with boosted combustion characteristics. The strategy utilizes fuel air mixing thermodynamics to fulfill higher in-cylinder energy maximization where adequate fuel distribution is managed in the combustion chamber. Regarding ECU development, integrated valve, intake airflow, as well…

Roll forming assemblies are generally neat and robust, but there are structural integrity risks involved too if the forming procedures and design features do not complement each other. Specifically, in solenoid valves, an imprecised roller crimping (or forming) adversely affect the desired magnetic performance of the valves. Furthermore, in-depth evaluations of the formed shape using hardware and lab testing are extremely challenging cost wise and time consuming as well. However, utilizing simulation technique such as finite element analysis (FEA) to understand the in-sights of roller formed assemblies of a solenoid valve (or other products) could be an effective way to minimize overall cost and time involved in the product development. Therefore, a three-dimensional non-linear FEA model of roller crimping simulation was established in ANSYS Workbench Mechanical, and the predicted results were correlated with real hardware data to prove the technique & process adopted. Then the design was improved computationally to eliminate the magnetic core’s flux-bridge distortion issue of a solenoid valve, and finally the design was validated through hardware testing.

Although supercharged system has been widely employed in downsized engines, the effect of supercharging on the intake flow characteristics remains inadequately understood. Therefore, it is worthwhile to investigate intake flow characteristics under high intake pressure. In this study, the supercharged intake flow is studied by experiment using steady flow test bench with supercharged system and transient flow simulation. For the steady flow condition, gas compressibility effect is found to significantly affect the flow coefficient (Cf), as Cf decreases with increasing intake pressure drop, if the compressibility effect is neglected in calculation by the typical evaluation method; while Cf has no significant change if the compressibility effect is included. Compared with the two methods, the deviation of the theoretical intake velocity and the density of the intake flow is the reason for Cf calculation error. For the transient intake condition, such increase of intake flow velocity with increasing intake pressure was found to be valid only at low engine speeds (2000 rpm). At high engine speeds (4000 rpm), however, flow velocity remains almost unchanged regardless of…