13th International Colloquium Fuels - September 2021 133 No-Harm Testing: Adaptation of HiL-testing to different types of liquid fuels and fuel component types Chandra Kanth Kosuru Tec4Fuels GmbH, Herzogenrath, Germany Simon Eiden Tec4Fuels GmbH, Herzogenrath, Germany Hajo Hoffmann Tec4Fuels GmbH, Herzogenrath, Germany Klaus Lucka Tec4Fuels GmbH, Herzogenrath, Germany Summary Tec4Fuels has developed hardware in the loop test benches which are being used for testing the fuel-material interaction for diesel and all diesel quality alternative fuels. They consist of passenger car fuel components such as in-tank pump, fuel filter, high pressure pump, rail and injector connected in a closed loop. These test benches have been capable of reproducing IDID (internal diesel injector deposits) with the diesel quality fuels. Currently, the scope of hardware in the loop testing is being extended to gasoline and gasoline quality alternative fuels. In addition to passenger car fuel components, the test benches are now capable to handle the heavy-duty equipment, marine engine components etc. Tec4Fuels has been part of several EU Horizon 2020 projects such as REDIFUEL, IDEALFUEL, and BMWi projects like C3-Mobility in the aspect of fuel-material interactions. In this regard, the current topic discusses the adaptation of hardware in the loop test benches to different alternative fuels and fuel components. This paper also includes the initial observations on the fuel component interactions, especially injector deposit formation. 1. Background Compatibility testing is an important aspect with regards to the introduction of novel fuels, their blends and additional additive packages. To introduce a new product into the market, its impact on the current and future infrastructure has to be analysed and necessary changes have to be made. The motor tests such as DW10 or XUD9 are effective for such testing but also expensive, very high fuel is required, and high infrastructure is demanded [1, 2]. In this aspect, a cost-efficient method with less fuel requirements and time saving, less infrastructure demanded methods would be a premium choice as an initial step before motor tests [3]. TEC4FUELS has developed such a non-engine hardware in the loop (HiL) test method This HiL method can test the compatibility of the FIE (Fuel injection equipment) components with as less as 30 litres of fuel and in just 100 h of effective runtime [3]. This methodology has already been introduced into different EU-Projects where new synthetic fuels are being developed and their compatibility tests are of prime importance [1, 4]. Current paper explains the principle of the method briefly and how it’s being adapted to different project requirements, along with some initial observations from the testing. 2. Hardware in the loop Test Method The principle involved in the current HiL test method is to have as close testing conditions as possible to the Engine test but in a simplified manner [2]. This was achieved by avoiding the combustion step of the engine tests. Due to the absence of combustion, the method allows us to collect back the fuel into the tank and reuse. This way a relatively smaller fuel volume can be used to test the compatibility of the FIE. Also, due to the absence of combustion the injector control required for the test method is much simpler, very less infrastructure requirements and highly versatile with the test conditions. This method also gives the advantage of incorporating variety of FIE components with a simple change in few test bench components. Figure 1 shows the P&ID diagram of the HIL test bench for diesel and diesel like fuels. 134 13th International Colloquium Fuels - September 2021 No-Harm Testing: Adaptation of HiL-testing to different types of liquid fuels and fuel component types In this test bench all the FIE components from in-tank pump, filter, high pressure pump, rail to injector is connected in series. The fuel is then injected into the reactor, where the fuel is allowed to condense and flow back to the fuel tank through a heat exchanger. To simulate the impact of combustion on the injector, the injector nozzle is heated to a required set temperature. Furthermore, the vibrations and exhaust gases involved due to combustion are missing. But lack of combustion has given more flexibility of the test conditions. Figure 1: P&ID diagram of a Diesel HiL system The test conditions are free to select including test runtimes from a continuous run to a cyclic test run. The fuel volume can be as low as 30 litres with the test run times reduced to just 100 hours of effective runtime. The test cycle is free to choose according to the requirement. The ON-OFF phases can induce more stress on the component and the fuel to estimate their long-term behaviour. The off-Phases are also important, to allow the fuel to cool down to as low as ambient conditions allowing the ageing products to settle down on the component surfaces. The infrastructure requirements for the testbench are rather simple which can avoid the commissioning challenges, the switching between different types of injectors can be achieved by a simple switch of the heating block, which fixes the injector to the reactor. Furthermore, this allows to investigate each component of the FIE system individually and continuously monitor their performance. Also considering the challenges of requiring 1000 litres of fuel for an engine test, this can be optimised by using as low as 30 litres for the entire test. This could be especially beneficial in the case of testing Novel fuels, where the production of 1000 litres for the engine test is a big challenge. Similarly for a short test of the impact of additive the fuel requirements can be significantly reduced. Furthermore, due to the use of same fuel in loop, this allows the fuel to degrade over time, and also gives an idea on how the fuel would behave in the long term and its impact of on the FIE system. Similar to the above-mentioned diesel test system, the sample principle is being used for a Gasoline HiL system and further, the principle is being adapted to different fluid testing systems such as shipping industry, E-mobility (cooling fluid testing), etc. 3. Initial observations In one of the current EU Projects, named as REDIFU- EL (Robust and Efficient processes and technologies for drop in renewable FUELs for road transport) a diesel like synthetic fuel is being developed using the syngas through a Fischer Tropsch synthesis. This fuel consists of a mixture of paraffinic components and a mixture of higher chain alcohol. The presence of alcohol mixture helps to reduce the emissions and also achieve an almost sootless combustions. The fuel shows a high potential of Drop In capability and is much similar to EN590 properties. In this project the developed REDIFUEL (RF) is being tested as pure component but also as a blend component with diesel B0 and B7. For testing the compatibility of this fuel an Euro4 FIE system has been used to estimate the Drop In capability in the current infrastructure. The test parameters are selected according to a nominal load condition. They are 1300 bar rail pressure, with an injector nozzle temperature varying from 230 °C and 280 °C, with injector control at 17 Hz frequency and 800 µs energizing time. The test has been run in cycle with 16 hours of on phase and 8 hours of break (in intervals of 4 h on and 1 hour break) to induce higher stress conditions for the fuel and the FIE. The pure and blend component (blend with B0) of the REDIFUEL has shown high compatibility with all the fuel components. The functionality of all the FIE components is intact, and no abnormalities have been detected. The mass flow rate through the inject or has also been constant throughout the test method. The alcohols are in general hygroscopic and lead to a rise in water content of the fuel, but the has not shown any impact on the component and all the components have shown full functionality after the experiment time. In a follow up test with the blend of B7 with the Redifuel, the injector has failed after 90 hours of testing. The initial blockage (no flow through the injector) was observed at almost 90 hours and after 100 hours the injector solenoid was failed due to the lack of flow. The test has been repeated twice to confirm the issue and the behaviour was reproduced the same way in both the cases. To solve the issue two types of DCA (deposit control additive) have been introduce into the blend in two different experiments. These additivities have solved the issue of injector blocking and lead to a smooth running of the injector after 100 hours of HiL testing. Also, the flow rate in this case was observed to the constant. In comparison between different blends, it has been determined that the inclusion of 7 % FAME had an impact in the failure. 13th International Colloquium Fuels - September 2021 135 No-Harm Testing: Adaptation of HiL-testing to different types of liquid fuels and fuel component types Figure 2: Dis-assembly of a Euro 4 injector. Figure 2 shows the dis-assembly of the faulty injector after the HiL test. The injector has been opened and check for deposits and the possible cause for the blockage. It has been observed that the Brass ring (Magnified on the right side) has been stuck, which should freely rotate to allow the fuel flow through the injector. This has led to the injector failure. The failure has been similar in repeated tests as well. Further information from the experts have indicate that this is a typical type of IDID (internal diesel injector deposits) that can occur in a long-term real-time operation. This implies that the HiL method can successfully reproduce the IDID and also been able to find a solution in the development phase of the fuel. In a different project, C3-Mobility, similar HiL test bench has been developed but for a Gasoline like fuel testing. In this project, Pure 2-Butanol and MtG are tested for their compatibility with the FIE of a gasoline engine. The test parameters were set at 250 bar rail pressure and injector parameters to 33 Hz frequency and 4 ms energizing time. These conditions are considered a as high load engine operation. The nozzle temperature is set to 150 °C as proposed according to a typical gasoline engine parameter. The tests were performed for 500 h of runtime in a cycle of On-Off phases. After the testing of different blends, it has been observed that Pure components if MtG, 2-Butanol and EU6 have shown no deposit formation. But the 50 % blend of 2-Butanol with the EU6 has shown deposit formation on the injector as shown in the figure 3. Figure 3: Comparison of injector nozzle between different experimentsKos Furthermore, the HiL testing is being adapted to a different fluid testing system. This method is also being developed for testing the Bio-HFO, a biofuel which is being developed for the marine applications in the project named as IDEALFUEL. Also, the HiL method is free to adapt from a domestic heating system to a E-mobility system. In the E-Mobility, the cooling fluids are subjected to higher stress to cool the engine components. This provides the scope of testing different cooling fluids for their durability, safety, operability and finally compatibility with different E-mobility systems. 4. Conclusion and Outlook The current study has shown how the test benches are capable of reproducing IDID, and also their flexibility of testing multiple components. This test method shows a good potential of being an initial screening method for novel fuels and additives before being implemented in complex or expensive motor tests. All the novel fuels are expected to be Drop-in capable, so that the transformation from production to market is smooth enough. In this regard, these non-engine test benches could be key in implementing into research. Currently, the method is being adapted to Marine and E-mobility sector and must further investigated its detailed potential of serving as a standard test procedure for the Novel engine components before being introduced into the market. References [1] C. Kosuru, H. Hoffmann, K. Lucka. OME: Fit-forpurpose-testing of alternative fuels on the specific topic of the evaluation of OME’s drop-in compatibility, 103 (2019). [2] Hoffmann H. A contribution to the investigation of internal Diesel injector deposits ([1. Auflage]). Shaker Verlag, Aachen (2018). [3] Hoffmann H, Sebastian Deist, Koch W, Lucka K. Development of a Non-Engine Fuel Injector Deposit Fuel Test: Results. [4] C. Kosuru, S. Eiden, H. Hoffmann, K. Lucka. Compatibility Studies of Alternative Fuels on Fuel System Components and Materials.