Numerical simulation to evaluate the influence of geometric parameters on the physical behavior of heat exchangers

In the present investigation, a methodology was developed by means of numerical simulation for the evaluation of the influence of the geometric parameters of the heat exchangers used in thermoelectric generation devices. The validation of the proposed methodology was carried out through experimental tests on a diesel engine test bench under four load conditions (2 Nm, 4 Nm, 6 Nm, and 8 Nm) and a constant speed of 3600 rpm. The results obtained show that the methodology proposed by means of the numerical simulation presents a high concordance with the behavior described experimentally. The deviation between the simulation predictions and the experimental results was less than 4%. Additionally, it was evidenced that the change in the geometry of the heat exchanger has a considerable impact on the parameters of heat flow and surface temperature. It was shown that a 50% reduction in fin distance causes an increase of 2% and 2.4% in the previous parameters. Through geometric modifications, the electrical power generated increased by 7.9%. In general, the methodology developed through numerical simulation allows the analysis of the physical, thermal, and hydraulic phenomena present in heat exchangers focused on use in thermoelectric devices.

Design and evaluation of an engine-in-the-loop environment for developing plug-in hybrid electric vehicle operating strategies at conventional test benches

Due to a large number of degrees of freedom and connected powertrain functionalities, the development of operating strategies for plug-in hybrid electric vehicles is an especially complex task. Besides optimizations of drivability, noise, vibrations and harshness as well as energy efficiency, the main challenge lies in ensuring emissions conformity. For this purpose, test vehicles are typically applied to achieve a realistic test and validation environment. However, operating strategy calibration using test vehicles has the drawbacks, that (i) it is very time consuming and cost intensive, (ii) it can only be conducted in late development phases and (iii) cannot be applied to reproducing driving loads for a valid comparison. To overcome these issues, this paper presents a consistent engine-in-the-loop approach combining real engine hardware and multiple software elements to represent PHEV behavior at the engine test bench. Thereby, an environment is created, which allows for realistic, flexible, cost efficient and reproducible testing. The effectiveness of the presented framework is evaluated by comparing relevant on-road measurements with their reproduction at the engine test bench. The results show that the vehicle on-road behavior can be replicated using the described testing environment. Particularly engine start/stop behavior and load levels—the core functionalities for operating strategy calibration—are matched. The proven level of realism in powertrain behavior enables further use cases beyond on-road measurement reproduction, i.e. varying individual component properties and observing real-world consequences at the test bench without the need for vehicle tests.

Engine test bench feasibility for the study and research of real driving cycles: Pollutant emissions uncertainty characterization

The future of Internal Combustion Engines in the automotive sector seems uncertain, to some extent due to the recent changes in type approval regulations. Current regulations have considerably reduced the engine pollutant emissions limits, as well as introduced more demanding testing conditions. The introduction of real driving cycles presented a challenging issue for car manufacturers when homologating their vehicles, since the traditional and undemanding NEDC (New European Driving Cycle) certification cycle has been replaced by sever cycles as WLTC (World Light Duty Test Cycle) and RDE (Real Driving Emissions). This document presents a methodology for implementing a RDE cycle in an engine test bench. Even knowing that the essence of RDE regulation is to assess actual driving conditions, reproducing RDE cycles in a test bench is of great interest, since the controlled and reproducible conditions that can be achieved in a laboratory lead to valuable information to understand engine behavior in real driving conditions, and therefore contribute to engine development. This document applies the most recent European Community regulation and sets the essential steps to carry out a RDE cycle in an engine test bench. Once the WLTC and RDE cycles were implemented, this study analyses the uncertainty and repeatability of the values obtained in successive repetitions of the test, carried out under the same conditions. Uncertainty values are obtained on the most representative parameters of engine operation, as well as pollutant emissions. One of the most relevant contributions of this study is to obtain the uncertainties of type approval pollutant emissions. As an example, the uncertainty obtained by applying the methodology described in this article on nitrogen oxide emissions (NOx), considered one of the most relevant pollutant emissions of diesel engines, has been extremely reduced, obtaining values of 3.13% and 3.9%, respectively for the RDE and WLTC cycles.

Assessment of an electrical coolant pump on a heavy-duty diesel engine

Hybridization of the drive train in commercial vehicles is a key solution toward meeting the strict future requirements to reduce carbon dioxide emissions within the European Union. In order to decrease fleet consumption a large number of different hybrid systems are already available in series in the passenger car sector. Due to the cheap and powerful 48 volt hybrid components and the lower hazard potential compared to high voltage, future commercial vehicles could also benefit from the 48V technology and contribute to lower fleet fuel consumption. Therefore, a complete 48V mild hybrid system was built on the diesel engine test bench as part of a research project. This paper highlights the utilization of a powerful 48V-motor to propel the coolant pump on a diesel engine of the 13-L commercial vehicle class. Three different drive variants of the coolant pump were implemented and measured on the diesel engine test bench. MATLAB®/Simulink®-simulations were conducted to assess the possible fuel savings in three different driving cycles. This paper provides a summary and interpretation of the measurement and simulation results. The simulation studies predict a decrease of fuel consumption of up to 0.94%. Furthermore, the additional advantages of electrified coolant pumps based on 48V are discussed.

THE EFFECTIVENNESS OF SOME PRACTICAL METHODS OF LOWERING THE BACKGROUND ACOUSTIC NOISE, PRODUCED BY THE ENGINE TEST BENCH TECHNOLOGICAL EQUIPMENT

When conducting acoustic researches and finishing works on combustion engines specialized technological equipment and tools mounted mainly in anechoic chambers are used. In order to ensure the high quality and objectivity of the research results of the sound fields produced by the research object it is crucial to achieve a sufficiently low parasitic background noise produced by technological equipment and tools of an engine test bench. The source of a high background noise re-emited to the anechoic chambers interior is structural vibrations of the solid objects of load carrying and flatsheet box-type structures of the bench. The article considers tested technical methods of improving vibroacoustics of load carrying and envelope structures of the engine test bench, which is in startup, commissioning and preliminary operation phase in the research center of a car manufacturer. Therewith there was a requirement to prevent any fundamental changes of the bench original basic construction, in order to minimize potential material and financial expenses for its reengineering process. Tested design solutions allow to reduce the level of parasitic noise disturbances, produced directly by the bench equipment in an anechoic chamber, up to 12 dBA.

Implementation of a 3.5 kW resistive load bank for a single-cylinder diesel engine test bench

This article presents the implementation of a 3.5 kW resistive load bank applied to a four-stroke single-cylinder diesel engine test bench that operates with an alternator. With this experimental test bench, it is possible to perform mechanical, thermodynamic, and polluting emissions studies in compression-ignited or induced internal combustion engines. Applying the quantitative research methodology, the design of the electric charging system is carried out. Power control circuits and safety elements are designed for the load back. CAD software is used to design the structure and casing considering anthropometric measurements. Also, finite element analysis (FEA) is incorporated to verify the structural and thermal design criteria. he implementation of an electrical and instrumentation acceleration system for sensing power and torque in low-displacement engines showed a measurement error of less than 1%. Similarly, the FEA allowed to quantify the maximum efforts and guarantee a safety factor above 5. With the characterization of the implemented sensors, a correlation coefficient of up to 99.97% was achieved. The power measurement displayed an error lower than 3%, which leads to a high characterization capacity of any thermal machine with equal power or less than the designed one.