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Experimental Evaluation of Steady State Performance of an Automotive Electric Supercharger

Università Degli Studi di Genova-Silvia Marelli, Vittorio Usai
  • Technical Paper
  • 2020-37-0008
To be published on 2020-06-23 by SAE International in United States
Nowadays, the electric supercharger for turbocharged downsized automotive engines is mainly used to improve torque at low engine speeds in order to obtain an improvement of the time to boost. These components are usually designed to fill the gap in terms of torque in transient operation caused by the main turbocharger with reference to the typical turbo lag issues. An advanced solution of the engine boosting system was taken into account, considering the adoption of an e-booster system coupled to a waste-gated turbocharger, typically adopted alone in order to provide a reduced turbo-lag, i.e. an optimized transient response of the system. In the experimental activity described in this work, the maximum speed of the e-booster used is about 70000 rpm, the maximum pressure ratio is 1.5 and the maximum power required on the shaft is less than 4 kW. The compressor unit have to be maintained in the idle condition in order to avoid excessive electric consumption and overheating problem when the boost given by this component is not required. In order to highlight the…
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Methodology to quantify the undesirable effects of the localized inefficiency of heat pick-up in suction line on an automotive air-conditioning system

Y.S.Sarath Reddy
Tata Motors Ltd-Suresh Tadigadapa, Santosh Ghorpade, Ankit Shukla
  • Technical Paper
  • 2020-28-0036
To be published on 2020-04-30 by SAE International in United States
The automotive application places very special demands on the air conditioning system. As is the case with any other process, system efficiency is very important and the automotive air-conditioning application is no exception. While the characteristics of all the major components in the air conditioning system like compressor, condenser, evaporator and blower contribute to overall system efficiency, localized inefficiencies do play a part and so must be kept to a minimum, especially in this day and age when extra emphasis is being paid on sustainability. One such phenomenon that contributes to the system inefficiency is heat pick-up in suction line. Since the temperature at the evaporator-outlet is quite lower than ambient and also its surroundings (steering system pipes and hoses, engine, air intake pipes and so on), the refrigerant picks up heat as it moves along the suction line up to the compressor inlet. This heat pick-up is detrimental to the overall system performance. Even though most of the automotive HVAC engineers are fairly aware of the undesirable effects of heat pick-up in suction line,…
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Dynamic behavior of in-cylinder pressure causing fatigue failure of reed valves

Subros Ltd.-Ankit Shukla, Paulson Parayil, Arun Kumar Goel, Kamal Sharma
  • Technical Paper
  • 2020-28-0031
To be published on 2020-04-30 by SAE International in United States
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…
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Application of Phase Change Materials (PCM) for reducing cabin heat load

Tata Motors Ltd-Mayank Manoj Dubey, Suresh Tadigadapa, Abhijit DUBE, Ankit Shukla, Anurag Maurya, Y.S.Sarath Reddy
  • Technical Paper
  • 2020-28-0037
To be published on 2020-04-30 by SAE International in United States
In regions like Indian Subcontinent, Gulf or Saharan & Sub-Saharan Africa, where the sunshine is abundant almost all year round, air-conditioning is an important aspect of vehicles (passenger cars, buses etc). Higher heat means higher cooling demand which means bigger AC system which in turn. Now AC compressor is a parasitic load on the engine like other auxiliaries. Upcoming emission norms will result in more stringent constraints on the power that can be made available to auxiliaries by engine. Moreover, one of the most frequent customer complaint in JD Power rating survey results of passenger vehicles is "AC cooling not fast enough". Hence, the proposed idea suggests a way reduce the air conditioning power consumption, without compromising on the cool-down performance by eliminating the heat load source itself. The best way to beat the heat and reduce cabin heat load is the stop the heat build-up itself. The present paper explores one such mean of reducing cabin heat build-up by leveraging latent heat properties of phase change materials and thus improving the air condition performance.With…
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A detailed study of prominent factors affecting evaporator frosting in a mobile air conditioning (MAC) system

Tata Motors Ltd-Prasanna V Nagarhalli, Shrikant M Awate, Mubeen Syed
Tata Motors, Ltd.-Anurag Maurya
  • Technical Paper
  • 2020-28-0014
To be published on 2020-04-30 by SAE International in United States
In an automotive air conditioning system, evaporator is well designed for effective heat transfer between refrigerant and air flowing over the evaporator. Hence, the better cooling and dehumidifying the incoming air. Sometimes, at the low ambient temperature and higher relative humidity conditions a frost is observed. It is accumulated over the evaporator and often become thicker enough to block the flow of air completely passing through the evaporator resulting in a rise in vehicle cabin temperature. Current work presents the probable causes of frost formation and their effects on the performance of evaporator and hence, the performance of the automotive air conditioning system. There are four major factors, thermistor poor response, undercharged and overcharged system, clogged air-filter, and also the type of compressor causing frost formation over the evaporator are considered for analysis. Current work presents the experimental analysis of the evaporator performance in the low ambient conditions with the above factors in different iterations. With the above analysis new methods and guidelines can be generated in order to avoid frost formation over the evaporator.
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Modeling of an Integrated Internal Heat Exchanger and Accumulator in R744 Mobile Air-Conditioning Applications

University of Illinois at Urbana-Champaign-Wenying Zhang, Predrag Hrnjak
  • Technical Paper
  • 2020-01-0153
To be published on 2020-04-14 by SAE International in United States
Carbon dioxide (CO2 or R744) is a promising next-generation refrigerant for mobile air-conditioning applications (MAC), which has the advantages of good heating performance in cold climates and environmental-friendly properties. This paper presents a simulation model of an integrated internal heat exchanger (IHX) and accumulator (Acc) using the finite volume method. The results are validated by a group of experimental data collected with different transcritical R744 mobile air-conditioner and heat pump (MHP) systems, and the error was within ±10%. The impacts of refrigerant mass flow rate and operating temperatures on the heat transfer rate of the IHX, improvement on refrigeration capacity and the liquid level in the Acc were studied. Results show that the net benefits of IHX are significant in AC mode, while it helps preventing flooding of the compressor in MHP mode. Also, the IHX heat transfer performance is more sensitive to evaporator exit quality and operating temperatures than it is to relative mass flow rate. The flow and liquid level in the accumulator is also described by the model.
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Validation of a Theoretical Model for the Correction of Heat Transfer Effects in Turbocharger Testing through a Quasi-3D Model

Politecnico di Milano-Gianluca Montenegro, Matteo Tamborski, Augusto Della Torre
Universita Degli Studi di Genova-Silvia Marelli
  • Technical Paper
  • 2020-01-1010
To be published on 2020-04-14 by SAE International in United States
In the last few years, the effect of diabatic test conditions on compressor performance maps has been widely investigated, leading some Authors to propose different correction models. The accuracy of turbocharger performance map constitute the basis for the tuning and validation of a numerical method, usually adopted for the prediction of engine-turbocharger matching. Actually, it is common practice in automotive applications to use simulation codes, which can either require measured compression ratio and efficiency maps as input values or calculate them “on the fly” throughout specific sub-models integrated in the numerical procedures. Therefore, the ability to correct the measured performance maps taking into account internal heat transfer would allow the implementation of commercial simulation codes used for engine-turbocharger matching calculations.In the paper the main results of a wide experimental activity are reported to provide a general understanding of heat transfer mechanism occurring in turbochargers and relationships for heat transfer rate useful to derive the adiabatic efficiency. The compressor steady flow performance maps were measured at different operating temperatures for compressor and turbine, with and without…
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On-Engine Performance Evaluation of New-Concept Turbocharger Compressor Housing Design

Imperial College London-Ricardo F. Martinez-Botas
Mitsubishi Heavy Industries, Ltd.-Takao Yokoyama, Yutaka Fujita, Motoki Ebisu
  • Technical Paper
  • 2020-01-1012
To be published on 2020-04-14 by SAE International in United States
Following the market demands in finding the niche balance between engine performance and legislation requirement, a new compressor scroll has been designed for small to medium size passenger cars. The design adopts a slight deviation from the conventional method, thus resulting in broader surge margin and better efficiency at off-design region. This paper presents the design of the new compressor scroll and its performance validation. The new compressor scroll is coupled to a standard wheel and tested on the cold gas stand followed by the on-engine testing. The testing program focused on back-to-back comparison with the standard compressor scroll, as well as identifying on-engine operational regime with better brake specific fuel consumption (BSFC) and transient performance. A specially instrumented 1.6L gasoline engine was used for this study. The engine control unit configurations are kept constant for both the compressor testing. The intake and exhaust manifold has been customized to fit the turbochargers and kept identical between the standard and new compressor scroll installations. The turbocharger with new compressor scroll design is found to work at…
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Development of Ultra-low-friction and Zero-leakage Mechanical Seal for High-Speed e-Mobility Shaft Sealing Applications

Eagle Industry Co., Ltd.-Yuichiro Tokunaga, Nobuo Nakahara, Masatoshi Itadani
  • Technical Paper
  • 2020-01-1090
To be published on 2020-04-14 by SAE International in United States
By the year 2020, EU legislation limits CO2 emissions for new passenger cars to a maximum of 95 g/km, and further reductions to 68 g/km are expected. Electric motors with high power density often need shaft cooling in combination with increased rotational speeds to boost efficiency. Especially, the low friction and the durability of the sealing faces is essential to overcome the severe friction condition of the high-speed rotation. This challenge can be solved by using the revolutionary GlideXTM sealing technologies. These seals feature advanced texturing, a new surface technology that enables microscopic flow control in the dynamic sealing faces. Advanced texturing reduces leakage to the level of insignificance and up to 90% less friction, compared to a non-textured mechanical seal. The advanced texturing allows for a thin liquid-sealing film between the sealing faces. The liquid lubrication becomes dominant at low speeds; at high speeds, the gas lubrication becomes dominant by preventing the liquid from flowing into the sliding surfaces. As a result, the seal can keep low friction in both low- and high-speed rotations…
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Impact of Active-Grille Shutter Position on Vehicle Air-Conditioning System Performance and Energy Consumption in Real World Conditions

FCA Canada Inc.-Shankar Natarajan, Pooya Mirzabeygi
FCA US LLC-Michael Westra, Kumar Srinivasan
  • Technical Paper
  • 2020-01-0947
To be published on 2020-04-14 by SAE International in United States
Active grille shutter (AGS) in a vehicle provides aerodynamic benefit at high vehicle speed by closing the front-end grille opening. At the same time, this causes lesser air flow through the cooling module which includes the condenser. This results in higher refrigerant pressure at the compressor outlet. Higher head pressure causes the compressor to work more thereby possibly negating the aerodynamic benefits towards vehicle power consumption. This paper uses a numerical method to quantify the power consumed by the vehicle in different scenarios and assesses the impact of AGS closure on vehicle energy consumption. The goal is to analyze the trade-off between the aerodynamic performance and the compressor power consumption at high vehicle speeds and mid-ambient conditions. These so called real world conditions represent high way driving at mid-ambient temperatures where the air-conditioning (AC) load is not heavy. AC system which includes the refrigerant loop and vehicle cabin is modeled using 1D methodology and its performance simulated at system level. AC system performance is analyzed under steady state as well as transient conditions. Power consumption…