Fuel Economy Benefit of Active Grille Shutters for Real World, Worldwide Harmonized Light Vehicles Test Procedure, and Real Driving Emission Cycles

The introduction of Bharat Stage VI emissions level (BSVI) emission directives, the upcoming corporate average fuel economy (CAFE) regulations, and the ever-increasing cost of fuel have been bringing more focus, research and development (R&D) efforts into improving engine efficiency, fuel economy, performance and reducing carbon dioxide (CO₂) emissions. The Worldwide harmonized Light vehicles Test Procedure (WLTP) emissions regulation, Worldwide harmonized Light vehicles Test Cycles (WLTC) and Real Driving Emissions (RDE) have been introduced.

Active grille shutter (AGS) design and implementation has been discussed in this paper, a work that Tata Motors European Technical Centre (TMETC) has led for Tata Motors, and we have found that it improves the vehicle fuel economy in the real world. This work has been a part of the bouquet of programs TMETC is championing as a part of the new vehicle and powertrain technology introduction. The program of work includes vehicle efficiency; fuel economy improvement, starting from optimizing current energy balance; vehicle level performance; investigation of parasitic losses; and introducing technologies, which can crawl back losses and increase the efficiency, thereby improving real-world fuel economy while reducing emissions.

For any efficiency improvement activity, understanding the baseline energy balance (Figure 1, engine energy balance on engine dynamometer) is paramount, it helps develop an efficiency improvement roadmap and also helps decide on the sequence of technology interventions at different levels (powertrain, vehicle, etc.) Depending on technologies, some interventions with minimal changes and costs have the potential to achieve up to 1-2% fuel economy benefit. These technology interventions can help recover some of the identified losses (Sankey diagram, Figure 2) and convert them as usable energy to do work, thereby reducing fuel consumption. At TMETC, test bed work (Figure 1) is an important part of the strategy as it not only helps identify improvement opportunities but also enables technology integration studies and initial developmental work before migrating the engine onto the vehicle. Some of the recent range of technology interventions demonstrated by TMETC include a patent-filed integrated advanced-cool charge air cooler (CAC), a patent-filed engine zonal cooling concept. Other interventions like innovative injection strategies, water jacket optimization, advanced calibration, airpath optimization, various emission improvement strategies, and a range of vehicle-level new technology interventions have also been developed in-house to improve fuel economy and performance on a range of Tata production vehicles.

One such vehicle-level intervention for fuel economy improvement is AGS. In the current paper, the process of developing and refining AGS from concept design to developing an innovative in-house control logic to its implementation has been described. A Tata Nexon 1.2 TC (small SUV, Petrol) current production vehicle has been used to demonstrate the benefits of this technology, including in sign-off conditions (conducted at MIRA, UK), on road conditions in the United Kingdom (UK), and on road high-altitude (Granada) and high-ambient temperature tests in Spain. The various virtual methods, tests, development, and calibration techniques to evaluate the technologies have also been discussed. The controls logic is calibrated for optimal fuel consumption benefit on the WLTP tests. We have found a fuel economy improvement of 1.5% in the WLTC, which can be attributed to the combined effects of quicker warm-up, reduced engine friction, aerodynamic load. The benefits in real driving conditions are dependent on several factors such as the ambient temperature; the vehicle speed; heating, ventilation, and air conditioning (HVAC) setting; soak conditions; or driving mode. Experimental results showed an overall 2% benefit considering multiple road tests and gains over 4% for some on-road test conditions.