## 1 Introduction
By providing information about the mass flow rate and isentropic efficiency, they solve the system of equations by assuming a quasi-steady behavior. In the case of double entry turbines, the steady flow map under full admission condition (where the flow is the same in both entries of the turbine) is not enough for simulation purposes. In reality, the exhaust pulses feeding each entry of the turbine will be timed so that they are out of phase with each other; as a result, double entry turbines spend little time in full admission and the majority of the time with unequal flows in their entries. Therefore, the turbine maps should also cover the necessary flow conditions such as unequal and partial admissions between their entries [22]. Moreover, the addition of the second inlet to the turbine solute brings extra complexity in determining the steady-state turbine performance parameters. Addressing this, in previous work [12], a detailed analysis of experimental data and how to process the performance parameters of twin-entry radial-inflow turbine was shown for different steady flow admission conditions. Furthermore,an overview of the previous work is presented in this paper and the same techniques were applied to process the experimental data of a dual-volute turbocharger. Many methods for mean-line modeling of twin-entry turbines are available in the literature. However, at partial and unequal admission conditions, the prediction of efficiency from the models seem to be very difficult to obtain [32]. [PERSON] et al. [33] developed a twin-entry turbine model by modifying the one-dimensional equations, which are used to analyze the flow in single entry turbine. In addition, the loss models of single entry turbines were applied to the twin-entry by making some changes. By doing this, some predicting results were obtained. However, the authors pointed out that the calculated efficiency and the mass flow are overestimated. In the case of partial admission conditions, there was a remarkable difference between predicted and experimental data. [PERSON] et al. [34] developed a model for twin-entry turbines and solved it using a gas dynamics code. The pulse flow performance of a twin-entry turbine under unequal and full admission conditions was analyzed, suggesting that, for full admission flow states, twin-entry turbine can be modeled as a simplified single entry model, whereas for unequal flows a more complex model is necessary. Moreover, the complete unequal admission maps are not always available because many gas stands are not capable of operating in those conditions. Addressing this, [PERSON] et al. [11] proposed a map-based method for predicting the partial and unequal admission flows in double entry turbines (both twin and dual) from a given full admission map. Based on the experimental data, two correlations were proposed, one for twin-entry and another for a dual-volute turbine, and they concluded that the twin-entry turbine characteristic agreed reasonably well with their approach. However, the correlation with the performance of a dual-volute turbine was less satisfactory. [PERSON] et al. [35] proposed a method for extrapolating from the full admission map of the dual-volute turbine to obtain the unequal admission performances of both efficiency and mass flow parameters. The model is dependent on three constants: one of them is used for predicting the efficiency ratio between the unequal and full admission data points and the other two are used for estimating the mass flow ratio parameter. The values of the constants are determined by using the minimal amount of unequal admission flow data at different turbine speeds. The study concluded with good agreement between the model predictions and experimental results. However, the analysis was restricted to one dual-volute geometry turbine and it is not sure whether the same results can be found for another similar turbocharger without further experimental campaigns.