Pressure Ratio Turbocharger Research Articles

Thermodynamic and Comparative Analysis of Ejector Refrigeration Cycle and Absorption Refrigeration Cycle Integrated Wet Ethanol-Fueled HCCI Engine for Cogeneration of Power and Cooling

Abstract This study attempted for the proposal and analysis of a combined cycle that consists of a wet ethanol-fueled and turbocharged homogeneous charge compression ignition (HCCI) engine coupled to ejector refrigeration cycle (ERC) and absorption refrigeration cycle (ARC) for the simultaneous generation of two distinct outputs, namely, power and refrigeration. Both first and second laws of thermodynamics were employed to develop a thermodynamic model, which has been applied to investigate the performance of combined cycle. Furthermore, performance of the combined cycle for ERC versus ARC was compared and assessed after altering operating parameters (turbocharger pressure ratio, turbocharger compressor efficiency, ambient temperature, and the entrainment ratio of ERC and generator temperature of ARC) to study their effect on engine power output, refrigeration load, exergy of refrigeration, and energy and exergy efficiencies of the cooling-power cogeneration cycle. Results show that the elevated pressure of turbocharger results in the enhancement of HCCI engine power and increase of the refrigeration of thermal load, simultaneously. However, the increasing ambient temperature shows the decline of HCCI engine efficiencies and energy efficiency of cogeneration, while the cogeneration cycle exergy efficiency is found increasing. Furthermore, the results are reported for the refrigeration performed by lithium bromide–water (LiBr–H2O)-operated ARC, and R134a- and R290-operated ERC, respectively. Mapping of exergy destruction for the presented cogeneration cycle discovered HCCI engine, boiler of ERC, generator of ARC, and catalytic convertor as the components of significant exergy destruction. Entrainment ratio and type of refrigerant employed in ERC and the generator temperature of ARC show a marginal impact on the COPs of these cycles.

Proposal and analysis of a novel cooling-power cogeneration system driven by the exhaust gas heat of HCCI engine fuelled by wet-ethanol

A novel combined power and cooling cycle consisting of the ejector refrigeration cycle (ERC) and organic Rankine cycle (ORC) is proposed to enhance the overall efficiency of wet-ethanol fuelled homogeneous charge compression ignition (HCCI) engine. The proposed combined system of cooling-power cogeneration was simulated by Engineering Equation Solver (EES) software. Combined system responses to altering the operative conditions on the energy and exergy performances are ascertained to obtain guidance for system design. The results are computed for R134a, R290, and R600a working fluids. Increase in turbocharger pressure ratio from 2.5 to 3.5 raises the thermal efficiency of cooling-power cogeneration from 47.87% to 50.09% when R134a is used as working fluid. Cooling capacity and exergy of refrigeration are decreased by greater than 2.0% in case of R134a operated system when the vapor generator pressure is elevated from 1800 kPa to 2200 kPa. Increase in evaporator pressure of ERC from 327.4 kPa to 348.7 kPa is greatly beneficial to thermodynamic performance of cogeneration and its cooling capacity is improved by 11.34% when R134a is utilized as the working. When PEvap rises from 175.7 kPa to 186.9 kPa and R600a is employed as the working fluid, the cooling capacity is increased by 12.58%.

Impact of Turbocharger Compressor Pressure Ratio on Diesel Engine Performance and Nitrogen Oxides Emissions

Turbochargers is used on several engines since 1962, to gain greater power output. This paper presents a study of the impact of the turbocharger pressure ratio on diesel engine performance and nitrogen oxides (NOX) emissions. A series of simulation experiments were carried out by using Diesel-RK software on variable turbocharger pressure ratio diesel engine. Diesel-RK is known as a very good open source software for youthful researchers, since it is free and talented of simulating combustion and thermodynamics of diesel engines very well. The simulated results showed that, turbocharger pressure ratio (PR) is an important parameter which affects directly on engine performance, engine brake power (BP) increased when pressure ratio increased. At 2500rpm and pressure ratio equal to 1.5 the BP increment about 27.4% when compared to natural aspirated (NA) engine. More increment about 55% is achieved by increasing the pressure ratio to 2.5. Though the specific fuel consumption (SFC) reduced as the pressure ratio increased. At 4000rpm and pressure ratio equal to 1.5 the SFC reduction about 5% when compared to NA engine. More decrement rate in the SFC rate about 7% is achieved by increasing the turbocharger pressure ratio to 2.5. The brake thermal efficiency (BTE) also increased as the pressure ratio increased, due to increase in power. At NA engine and 3000rpm, the BTE is found to be 32.5%, while at PR = 1.5, the BTE is equal to 33.9% and the BTE at the PR equal to 2.5 is increased to 33.8%. On the other hand engine NOx emissions increased as the pressure ratio increased, at 3000rpm and PR equal to 1.5, the NOX rate increased at a rate of 20% when compared to the emissions of NA engine. NOX emissions continuously increased and reached more than 42% with PR equal to 2.5 when compared to NA engine. Turbocharger gives the small displacement engines much more power relative to their size e.g. PR equal to 2.5, turbochargers run off energy of exhaust gases that is always lost by the NA engines, so the recovery of this energy develops the engine efficiency.

三菱重工製過給機の変遷

三菱重工製過給機の変遷

Exergetic examination of a hydrogen enriched compressed natural gas fuelled homogeneous charge compression ignition engine

A second-law based exergetic study is undertaken for a parametric examination of CNG fuelled HCCI engine. The effects of change in equivalence ratio, turbocharger pressure ratio, ambient temperature, and hydrogen enrichment on the engine performance are investigated through energy and exergy efficiencies.

Effects of blade bowing on the performance of a high pressure-ratio turbocharger centrifugal compressor with self-recirculation casing treatment

The effects of blade bowing on the performance of a high pressure-ratio turbocharger centrifugal compressor were studied by experiments and numerical simulation. The results showed that the negative bowing was capable of increasing the choke mass rate and the efficiency but decreased the surge mass flow rate, while the positive bowing had the opposite effects. When coupling with the self-recirculation casing treatment, the surge mass flow rate of the compressor with negative bowing blade was almost identical with that of the prototype, while the choke mass flow rate was still larger, and the total effect contributed to an increase of the stable flow range by 5.85% at design speed. Besides, the flow mechanism of the coupling effects of blade bowing and self-recirculation casing treatment was discussed.

The Thermodynamic Study of Turbocharger Pressure Ratio and Ambient Temperature Variation on Exergy Destruction Estimation of Homogeneous Charge Compression Ignition Engine Cogeneration System

Homogeneous Charge Compression Ignition (HCCI) technology is different from conventional combustion technologies. It has the combination of lean and premixed fuel air mixture and charge is compression ignited so it has multiple ignition points throughout the combustion chamber thus eliminating the high peak temperature inside the combustion chamber. This new engine technology is helpful in production of ultra low NO and particulate emissions. The use of lean and X unthrottled operation yields higher efficiency and better fuel economy also. In this paper, a new HCCI engine combined cycle cogeneration system is proposed and studied. The system is equipped with turbocharger, fuel vaporizer, engine, catalytic converter, different components of Organic Rankine cycle (ORC) and further heat recovery steam generator (HRSG) for waste heat utilization from the exhaust gases to obtain process heat. An exergy analysis is applied to the different components of HCCI engine cogeneration system to examine the thermodynamic losses in terms of exergy destruction and the effect of ambient temperature and turbocharger pressure ratio is obtained. The result shows a ranking among the components of the system on the basis of thermodynamic losses or the exergy destruction. This paper shows how an exergy method can yield effect of ambient conditions and design parameters values to reduce losses in various components of HCCI engine cogeneration system.

A novel experimental method to evaluate the impact of volute’s asymmetry on the performance of a high pressure ratio turbocharger compressor

All components of a turbocharger compressor are axisymmetric except for the spiral-shaped, gas-collecting overhung volute. In this paper, a novel experimental method to evaluate the impact of the volute’s asymmetry on centrifugal compressor performance is proposed and applied to a high pressure-ratio turbocharger compressor. This method can isolate the impact of the volute’s asymmetry on the compressor performance for the first time. Experiments prove the considerable impact of the volute’s asymmetry on the compressor performance, especially the stability and efficiency. The impact of the volute’s asymmetry on compressor stability correlates with rotational speed and thus with the pressure ratio, constricting the stable flow range by up to 47 percent and decreasing the maximum efficiency by 4.8 percent at the design speed. The results provide evidence to exploit the potential of intrinsic non-axisymmetric flow induced by asymmetric volute to improve the performance of turbocharger compressor with a high pressure ratio.

Second Law Assessment of a Wet Ethanol Fuelled HCCI Engine Combined With Organic Rankine Cycle

In this study, first and second law analyses of a new combined power cycle based on wet ethanol fuelled homogeneous charge compression ignition (HCCI) engine and an organic Rankine cycle are presented. A computational analysis is performed to evaluate first and second law efficiencies, with the latter providing good guidance for performance improvement. The effect of changing turbocharger pressure ratio, organic Rankine cycle (ORC) evaporator pinch point temperature, turbocharger compressor efficiency, and ambient temperature have been observed on cycle’s first law efficiency, second law efficiency, and exergy destruction in each of its component. A first law efficiency of 41.5% and second law efficiency of 36.9% were obtained for the operating conditions (T0 = 300 K, rp = 3, ηT = 80%). The first law efficiency and second law efficiency of the combined power cycle significantly vary with the change in the turbocharger pressure ratio, but the change in pinch point temperature, turbocharger efficiency, and ambient temperature shows small variations in these efficiencies. Second law analysis demonstrates well how the fuel exergy is used, lost, and reused in all of the cycle components. It was found that 78.9% of the total input exergy is lost: 2.0% to the environment in the flue and 76.9% due to irreversibilities in the components. The biggest exergy loss occurs in the HCCI engine which is 68.7%, and the second largest exergy loss occurs in catalytic converter, i.e., nearly 3.13%. Results clearly show that performance evaluation based on first law analysis alone is not adequate, and hence more meaningful evaluation must include second law analysis.

Investigation of a wet ethanol operated HCCI engine based on first and second law analyses

Abstract In this paper, a conceptual wet ethanol operated homogeneous charge compression ignition (HCCI) engine is proposed to shift the energy balance in favor of ethanol. The investigated option, HCCI engine is a relatively new type of engine that has some fundamental differences with respect to other prime movers. Combined first and second law of thermodynamic approach is applied for a HCCI engine operating on wet ethanol and computational analysis is performed to investigate the effects of turbocharger compressor ratio, ambient temperature, and compressor adiabatic efficiency on first law efficiency, second law efficiency, and exergy destruction in each component. First law and second law efficiencies are found to be an increasing function of the turbocharger pressure ratio, while they are found to be a decreasing function of the ambient temperature. The effect of turbocharger pressure ratio on exergy destruction is found to be more significant than compressor efficiency and ambient temperature. Exergy analysis indicates that maximum exergy is destroyed in HCCI engine which represents about 90.09% of the total exergy destruction in the overall system. Around 4.39% exergy is destroyed by the process of heat transfer in fuel vaporizer and heat exchanger. Catalytic converter contributes about 4.08% of the total exergy destruction. This will provide some original information on the role of operating variables and will be quite useful in obtaining the optimum design of ethanol fuelled HCCI engines.

Turbocharger-Design Effects on Gasoline-Engine Performance

Specification of a turbocharger for a given engine involves matching the turbocharger performance characteristics with those of the piston engine. Theoretical considerations of matching turbocharger pressure ratio and mass flow with engine mass flow and power permits designers to approach a series of potential turbochargers suitable for the engine. Ultimately, the final choice among several candidate turbochargers is made by tests. In this paper two types of steady-flow experiments are used to match three different turbochargers to an automotive turbocharged-intercooled gasoline engine. The first set of tests measures the steady-flow performance of the compressors and turbines of the three turbochargers. The second set of tests measures the steady-flow design-point and off-design-point engine performance with each turbocharger. The test results show the design-point and off-design-point performance of the overall thermodynamic cycle, and this is used to identify which turbocharger is suitable for different types of engine duties.

Investigation of Diesel Engine and Turbocharger Interaction

The authors are concerned with the proper provisioning of turbochargers and fuel-injection equipment for diesel engines, particularly in the automotive class. Medium-speed engines are run at high mean effective pressures and there is a tendency towards similar outputs in automotive engines. Because of transmission demands these outputs will be required over a wide speed range and the relation of engine air and fuel requirements is examined. The simple turbocharger is not ideally suited to wide range matching and the extent of the compromise inherent in fixed geometry compressors and turbines is discussed. In order to survey engine, turbocharger, and fuel-system interactions tests are reported where turbocharger limitations are avoided by the use of two units in series. Engine operating limits were selected on the basis of safe engine factors and the output assessed with respect to the principal variables of turbocharger pressure ratio and engine compression ratio. The resulting compromise between high cylinder pressures and smoke control tended towards a traction-type torque curve with a higher-than-conventional fall-off in torque with speed. A suggestion was verified that smoke occurred at higher air/fuel ratios as the charge density increased. Nevertheless accepted methods of heat-release prediction from rate of injection characteristics were not affected by variation in charge density.

Aerothermodynamic Considerations Involved in Turbocharging Four and Two-Cycle Diesel Engines

Abstract The turbocharged engine is, in effect, a compound engine in which the engine itself handles the high-pressure end of both compression and expansion, while the exhaust-turbine-driven compressor takes care of the low-pressure end. The turbocharger pressure ratio determines the division of work between high-pressure and low-pressure components, and the value of this pressure ratio governs, to a large extent, the values of all engine performance variables. In this paper the interrelationships between all of these variables are discussed, and curves are presented giving, numerically, the interdependence, one on the other, of turbocharger pressure ratio, thermal loading, specific fuel consumption, and turbocharger combined efficiency, with and without intercooling. The aerothermodynamic situation of the two-cycle engine is treated separately, with emphasis on the all-important flow-handling ability of the engine. This ability is defined by the concept of the “gas change process merit ratio,” and, by means of a series of curves, the specific engine air flow is given for different merit ratios and different turbocharger combined efficiencies for a range of turbocharger pressure ratios. Finally, for both two-cycle and four-cycle engines, the importance of good matching between engine air consumption characteristics and turbocharger air delivery characteristics is discussed, and as a criterion for this matching the engine operating line, as it appears superimposed on the compressor characteristic curves, is used.